In a medium bowl, mix the marinara sauce with the remaining 1/4 cup of cream. Spoon half of the sauce into a 9-by-13-inch oval baking dish. Stuff each shell with a heaping tablespoon of the filling and nestle in the sauce. Spoon the remaining sauce over the shells and scatter the mozzarella on top.

Cover the baking dish and bake for about 45 minutes, then uncover and bake for 15 minutes longer, until bubbling and the pork is cooked through. Let stand for 10 minutes, then garnish with parsley and serve.